You can make the argument that all fiction is autobiographical -- that is, a fiction writer puts his or her own thoughts, feelings, emotions, etc., into the characters and situations he or she creates on the page.
But I've never considered myself an autobiographical writer. Sure, things pop up that can be traced to my life (character names, certain events), but I've always steered clear of basing my fiction on what has happened in my life. I'm more of a "I like to make stuff up" writer vs. a "write what you know" writer.
My story "A Brief Survey" (published by Metazen) is the most autobiographical story I've ever written. In fact, it might not even be called fiction.
The narrator is me; the scenes and emotions are straight from the past few years, during which it's seemed as if someone was sick or dying or being diagnosed with an illness every other month; and the part from the notebook is an almost verbatim of what I wrote right before and after my father died.
I'm not sure how it feels yet, to have something so "me" out in the world. But it seemed like a story that needed to be told. I only hope that I told it well...